Method of manufacturing flow-detecting granulated coloring magnetic particles

ABSTRACT

THE METHOD OF MANUFACTURING FLAW-DETECTING GRANULATED COLORED MAGNETIC PARTICLES COMPRISING THE STEPS OF ADDING IRON DUST, A COLORING AGENT, AND A BINDER TO A SOLVENT. THESE INGREDIENTS ARE BLENDED TO MAKE A MIXED LIQUID MATERIAL AND SAID MIXED LIQUID MATERIAL WITH A SEPARATION AGENT THEREIN IS SPRAYED WITH THE IRON DUST. THEN THE MIXED LIQUID MATERIAL IS SEPARATED INTO PARTICLES OF IRON DUST COATED WITH THE COLORING AGENT SO AS TO PRODUCE COLORED MAGNETIC PARTICLES.

p 1971 KAZUQ HONJO 3,573,979

METHOD OF MANUFACTURING FLAW'DETECTI GRANULATED. I COLORING MAGNETIC PARTIC Filed May 8, 1968 LLMWWV K W IIQXQEAIIITOR. 9m

United States Patent 3,573,979 METHOD OF MANUFACTURING FLOW-DETECT- ING GRANULATED COLORING MAGNETIC PARTICLES Kazuo Honjo, 7-17, 4-chome, Koshienguchi,

Nishinomiya, Hyogo, Japan Filed May 8,1968, Ser. No. 727,501

Claims priority, app li2cation9gapan, July 1, 1967,

Int. Cl. H01t 1/56; 344a 1/08 US. Cl. 117-234 6 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to the method of manufacturing flaw-detecting granulated coloring magnetic particles for testing a defective workpiece.

-If an electric current is passed through a magnetic body or workpiece by a magnetic flaw detecting device, when there are cracks or pin-holes on the surface or in parts slightly below the surface of such magnetic metallic body or workpiece, the magnetic reluctance of a defective part is greater than that of other parts which are not defective so that only the defective part shows a magnetic flux deflection, while magnetic flux leakage into air takes place. When the magnetic flux leaks from the interior of the magnetic metallic body into the air, magnetic poles will be produced in that defective part and if magnetic particles are dispersed over the defective part, they will be attracted by the magnetic poles and attached thereto in a wider area than that of the defective part, so that any minute defect which is imperceptible to the human eye will become visible plain. In other Words, a visible lump is formed.

The magnetic particles utilized for the above-mentioned purpose are generally colored so as to be clearly visible when they are retained over a defective part.

The manufacturing of such particles has been described, e.g., in Robert C. Switzer US. Pat. No. 2,267,999. In making these particles according to methods of the prior art, because of the pulverizing of a dried mass so as to form the magnetic particles, a sizable quantity of the coloring agent attached to iron dust by means of a binder is exfoliated, so that the magnetic particles are imperfectly colored. Also, as the exfoliated coloring agent does not include iron dust, it attaches to parts other than the defective parts, so that confusion is caused.

The principal object of the present invention is to provide a method of manufacturing the colored magnetic particles without resorting to the conventional process of the prior art.

Another object of the invention is to provide a method of making all magnetic particles colored without fail.

Still another object of the invention is to provide colored magnetic particles of large particle size shaped like a true sphere or a nearly true sphere.

Yet a further object of the invention is to provide a method of obtaining colored magnetic particles which have a nearly uniform particle size that is appropriately large.

Patented Apr. 6, 1971 All the above-mentioned objects and the other objects of the invention as well as the advantages over the prior art will become apparent from the following description thereof.

Generally speaking, the present invention contemplates the manufacturing of granulated colored magnetic particles by first adding one part of iron dust, a coloring agent and a binder to a solvent and blending to make a mixed liquid. The mixed liquid with the separation agent therein is sprayed over a second part of iron dust and the mixed liquid is then separated from the particles of the iron dust coated with the coloring agent, i.e., the colored magnetic particles and recovered from the liquid.

For a more detailed description of the invention, reference will now be made to the accompanying drawings wherein;

FIG. 1 is a partly illustrative longitudinal section of a device used for the manufacturing of granulated colored magnetic particles according to the invention.

FIG. 2 is a sectional view along the line 22 of FIG. 1.

In FIG. 1 is shown a tank 4 which has, when viewed in section, an inverted U-shape. Tank 4 is disposed over and is slightly smaller than a shallow tank 2 that has legs 1 and an outlet port 3 at its lower end, so that a chamber 5 is formed. In centrally opposed parts of the chamber wall and penetrating into the inside through the side walls of tank 4 are sets of sprayers 6 for the mixed liquid material and circularly arranged sprayers 8 for the separation agent, which have several nozzles 7 centering round the sprayer 6 and are disposed opposite each other. The mixed liquid material 9 is sprayed out of sprayer 6 by means of air pressure. Sprayer 6 is provided with a feed pipe 10 for the mixed liquid material and also a feed pipe 11 for compressed air. On the inside of the upper wall of tank 4, there is a dispersing pipe 13 for the separation agent, which runs circularly along the whole side wall, e.g., the inside upper end part of the circumferential wall of the tank 4 and, which has a number of the nozzles 12. Both the sprayer 8 for the separation agent and the dispersing pipe 13 for the separation agent use the same feed pipe 14 for the separation agent, so that the same separation agent 15 is sprayed out of the sprayer 8 as well as the dispersing pipe 13.

A tank 17 provided with short legs 16 is arranged beside the tank 2, and an outlet pipe 18 leads from the side wall of tank 2 and bends downwards so as to flow liquid into tank 17. The mixture of the coloring magnetic particles and the separation agent received into the tank 2 through the intermediary of the outlet pipe 18 is received by the tank 17, on the side wall of which is arranged an exhaust pipe 21 provided with a cock 20.

The mixed liquid material 9 is obtained by adding to a solvent, iron dust, a coloring agent and a binder and blending the ingredients by a stirrer, while further adding thereto a setting agent, if necessary, and then dispersing the ingredients well by the use of a colloid mill. For the iron dust to be made into magnetic particles, carbonyl iron, reduced iron, electrolytic iron dust, black magnetic iron or red magnetic iron may be used. Particularly, the carbonyl iron powders are suitable, because their shape is spherical and their particle size is uniform. The grain size of these iron dust particles should be aboutl to about 20g. A coloring agent is used to make the magnetic particles plainly visible to the human eye and this coloring agent includes both the pigment and the dyestuff. As the pigment, any colored inorganic pigment can be used. For instance, chrome yellow, chrome red and titanium white etc. can be used. It is also convenient to use fluorescent pigments such as 9,10-dianilinoanthracene and Z-hydroxyl-naphthaldazine. For the dyestuff, the basic dyestuffs are used. Especially, the dyestuif Rhodamine B is preferable.

It is red and, when irradiated by ultraviolet rays, it will shine in an orange color resulting in an increase in visibility. The color of the coloring agent should be in contrast to that of the objects to be inspected. For the binder, thermo-setting resins such as epoxide resin, butyrated melamine resin, butyrated urea resin or a thermo-plastic resin such as vinyl chloride and cellulose derivatives such as cellulose acetate and nitro-cotton etc. can be used. When the thermo-setting resin is used for the binder, it Will be necessary to add a setting agent such as a polyamide or the phosphoric acid. But, it will not be necessary to do so, when a thermo-plastic resin or the cellulose derivatives are used. For the solvent, any usual organic solvents can be used, but it is preferable to use a solvent from the ketone group, especially the methyl ethyl ketone. The most preferable mixture ratio of iron dust, coloring agent and binder is: iron dust about 15 to about 70%, coloring agent about to about 50% and binder about to about 40%. When the fluorescent pigment is used for the coloring agent, its compounding ratio may be comparatively small, because it will shine and be easily visible to the human eye. Conversely, when the white pigment is used, its volume must be larger in order to completely whiten the surface of the magnetic particles. A suitable quantity of the setting agent should be used according to the kind of the binder. All these compounded elements are dispersed in the solvent to enable the mixed liquid material 9 to be passed to the sprayer 6 and through the feeder 10 of the mixed liquid material and then it is sprayed into the chamber 5 by means of air pressure of compressed air feeder 11. Because of the mixed liquid material 9 being sprayed as described, its viscosity should be prepared to be about 30 to about 150 centistokes, while the quantity of the solvent for the iron dust, coloring agent, binder and setting agent will be determined in accordance with the viscosity of the liquid material 9. On the other hand, the pressure of the compressed air should be controlled so as to be stronger than 4 kg./cm. so that when the mixed liquid material 9 is sprayed out of the sprayer 6, it may be dispersed into as many grain size units as possible. When the mixed liquid material 9 is sprayed into chamber 5, the separation agent is sprayed out of the sprayer 8 and the dispersing pipe 13 at the same time. For the separation agent, water, hot Water of about 160 F, vapor, petroleum, naphtha solvent, mineral turpentine and other liquids or vapor which can separate the particles of the iron dust from each other, can be used. Economically, however, water is preferable. When necessary for rapid hardening, hot water or vapor is used, because of their promoting action to harden the setting agent.

With regard to the use of petroleum, generally speaking, there are a dry and a wet process. By the dry process, the coloring magnetic particles are disposed over the workpiece to be inspected in a dry condition. In the wet process, the coloring magnetic particles are dispersed in water, wherein is added a marginal activator or petroleum.

When petroleum is used as the dispersing mordant in the wet process, the dispersion effects will be less than, if water is used as the separation agent. Consequently, it is often necessary to use petroleum as the separation agent. When, however, petroleum and an insoluble component such as methanol is used as the solvent, petroleum and an insoluble resin such as epoxide resin is used as the binder.

The mixed liquid material 9, sprayed out of the sprayer 6 is dispersed in the forms of grain units of iron dust or the assembly of several of these grain units, when all of the units are coated with the coloring agent by means of the binder, so that they are colored magnetic particles of a spherical or nearly spherical shape. Meanwhile, the solvent is volatilized before the coloring magnetic particles are deposited in tank 2 and the mixed liquid material becomes the coloring magnetic particles on account of its having been sprayed as described. These magnetic particles tend to get together during the sedimentation. The

separation agent 15 sprayed out of the several nozzles 7 of the sprayer 8 acts to prevent this tendency.

Thus, the separation agent 15 keeps contact with the mixed liquid material 9 that is sprayed. Since the spraying force of the liquid material 9 is stronger than the separation agent 15, the latter will be attracted to the former, which will be also deposited in tank 2 together with the respective grains of the coloring magnetic particles which are still adhesive. Solvent contained in the liquid material 9 will volatilize mostly when sprayed and completely volatilizes before the colored magnetic particles are held in the tank 2, into which a certain quantity of the separation agent 15 has been placed beforehand.

On the other hand, the separation agent 15 sprayed out of the dispersing pipes 13 that are circularly disposed, will fiow down continuously along the whole side wall or the inside of the circumferential wall of tank 4 and prevent the dispersing, and still adhesive, coloring magnetic particles from attaching to the inside of the tank 4.

The mixture 19 of the coloring magnetic particles and the separation agent held in tank 2 are received into tank 17 through the intermediary of outlet pipe 18 and, when a certain quantity is stored, the cock 20 is opened to transfer the material through exhaust pipe 21 to a centrifugal separator 21a. The separation agent is eliminated by the centrifugal separator to produce granulated coloring magnetic particles, the grain size of which are preferably 3-30 t. The grain size are preferably small, when the defect of the workpiece to be inspected is small, but it should be large, if the defects are large.

In the accompanying drawing, the sprayers 6 of the mixed liquid material and the sprayers 8 of the separation agent are fixed opposite to each other on the right and left walls of tank 4. These sprayers can be increased or decreased whenever so required. The separation agent 15 will be so sprayed as to center around the mixed liquid material 9. The separation agent 15 may be sprayed against the mixed liquid material 9 which will also be sprayed at the same time at right angles thereto or at some other angle, so that both spraying streams cross each other. The same result may be obtained, if tank 2 is previously sufiiciently filled with the separation agent 15, and the nozzles of the sprayer of the mixed liquid material are put into the separation agent 15 to spray the mixed liquid material therein.

In the aforementioned case, no sprayer of the separation agent is necessary. But, the injection pressure of the sprayer of the mixed liquid material should be greater than the pressure in the air. It should be controlled to be about 6.5 kg./cm.

The actual examples of the mixed liquid material and the products obtained by the method of the present invention are as follows, when the spraying pressure is 6.2 kg./cm. and water is used as the separation agent:

EXAMPLE 1 Mixed liquid material: Parts by weight, g.

6-9 of carbonyl iron as iron dust 20 Titanium white as the coloring agent 60 Epoxide resin as the binder 12 Polyamide as the setting agent 5 Methyl ethyl ketone as solvent 100 Product:

10-30/L of granulated white magnetic particles 92 EXAMPLE 2 Mixed liquid material: Parts by weight, g.

6-9 of carbonyl iron as iron dust 50 Chrome red as the coloring agent 65 Epoxide resin as the binder 50 Polyamide as the setting agent l0 Methyl ethyl ketone as solvent Product:

8l5 of granulated red magnetic particles 166 While preferred embodiments of the invention have been shown and described, many modifications thereof can be made by one skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. The method of manufacturing fluent colored magnetic particles, comprising the steps preparing a slurry of iron dust, a coloring agent, and a solvent dispersed binder; spraying said slurry into a chamber in one direction from a first source while simultaneously causing said spray to be contacted by a spray of a separation agent selected from the group consisting of water, water vapor, petroleurn, naphtha, and turpentine from a second source in a direction where the sprayed slurry and the sprayed separation agent will intersect at a location away from said first and second sources, and simultaneously spraying the walls of the chamber with said separation agent.

2. The method defined in claim 1 utilizing vapor as separation agent.

3. The method defined in claim 1 with petroleum as separation agent.

4. The method defined in claim 1 including the steps of spraying said liquid material and said separation agent in such a manner that their streams will cross at substantially a right angle.

5. The method of claim 1 wherein said liquid material is sprayed from opposite sides of a treating zone and at the same time, the separation agent is sprayed from a circumferential location so that said sprayed liquids should come into contact as little as possible at the spray sources.

6. The method defined in claim 1 utilizing water as separation agent.

References Cited UNITED STATES PATENTS 2,267,999 12/1941 Switzer 32438 2,643,243 6/1953 Dannenberg 117l05.5X 2,788,337 4/1957 Preiswerk et al. 117105. 5X 2,878,392 3/1959 Polito 250-71 3,042,616 7/1962 Brown 32438 3,054,751 9/1962 Blake et al. 117100X FOREIGN PATENTS 526,182 6/1956 Canada 117105.5 129,744 8/ 1945 Australia 117-1055 WILLIAM D. MARTIN, Primary Examiner M. R. P. PERRONE, 1a., Assistant Examiner U.S. Cl. X.R. 

